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Special Notice #198: Possible Outburst of GK Per

March 9, 2010: The old nova (1901) and x-ray source GK Per may be going into outburst. Reports beginning late on 2010 March 6 UT show it brightening from its minimum visual magnitude of about 13.1 to 12.3-12.4.

When GK Per went nova in 1901, its disk was destroyed. Eventually the disk was re-established, and dwarf nova-like outbursts were observed. After many years of quite similar- looking outbursts about 1100-1300 days apart, rising to about visual magnitude 10.1 in 24-30 days, and lasting 53-73 days, the last two outbursts were very different, with the September 2004 outburst coming only 940 days after the preceding outburst, taking over 60 days to rise to a maximum of 10.6, and lasting about 100 days, and the December 2006 outburst coming about 810 days later, rising only to magnitude 11.5 with oscillations to 12.2 before returning to minimum about 100 days after outburst. The current probable outburst is occurring about 1180 days after the last outburst, so it may show more typical outburst behavior, or it may do something completely unexpected. Close monitoring is extremely important.

Our assistance has been requested by Dr. Phil Evans, University of Leicester, England, who is observing GK Per with the Swift satellite and has requested Target of Opportunity (ToO) time on RXTE. Dr. Evans writes:

"I have an approved Swift ToO which will observe it 3 times a day for the next 4 days (looking for the change in X-ray characteristics) and then for 6 ks twice a week thereafter. It chose a bad time of year to go off so will be too close to the Sun for Swift from early April. I've also put in a ToO request with RXTE and we'll see what happens.

"The AAVSO archive on this object is stupendous and anything your observers can do to make it even better will of course be gladly received by the whole CV community."

Visual and CCD observers are urged to monitor GK Per closely and submit observations to the AAVSO International Database.

Recent observations of GK Per reported to the AAVSO International Database include: